Systemic Pharmacotherapeutic Treatment of the ACTA1-MCM/FLExDUX4 Preclinical Mouse Model of FSHD.

Aberrant expression of the double homeobox 4 (DUX4) gene in skeletal muscle predominantly drives the pathogenesis of facioscapulohumeral muscular dystrophy (FSHD). We recently demonstrated that berberine, an herbal extract known for its ability to stabilize guanine-quadruplex structures, effectively downregulates DUX4 expression in FSHD patient-derived myoblasts and in mice overexpressing exogenous DUX4 after viral vector-based treatment. Here, we sought to confirm berberine's inhibitory efficacy on DUX4 in the widely used FSHD-like transgenic mouse model, ACTA1-MCM/FLExDUX4, where DUX4 is induced at pathogenic levels using tamoxifen. Animals repeatedly treated with berberine via intraperitoneal injections for 4 weeks exhibited significant reductions in both mRNA and protein levels of DUX4, and in mRNA expression of murine DUX4-related genes. This inhibition translated into improved forelimb muscle strength and positive alterations in important FSHD-relevant cellular pathways, although its impact on muscle mass and histopathology was less pronounced. Collectively, our data confirm the efficacy of berberine in downregulating DUX4 expression in the most relevant FSHD mouse model. However, further optimization of dosing regimens and new studies to enhance the bioavailability of berberine in skeletal muscle are warranted to fully leverage its therapeutic potential for FSHD treatment.

Shaping Drosophila eggs: unveiling the roles of Arpc1 and cpb in morphogenesis.

The Drosophila egg chamber (EC) starts as a spherical tissue at the beginning. With maturation, the outer follicle cells of EC collectively migrate in a direction perpendicular to the anterior-posterior axis, to shape EC from spherical to ellipsoidal. Filamentous actin (F-actin) plays a significant role in shaping individual migratory cells to the overall EC shape, like in every cell migration. The primary focus of this article is to unveil the function of different Actin Binding Proteins (ABPs) in regulating mature Drosophila egg shape. We have screened 66 ABPs, and the genetic screening data revealed that individual knockdown of Arp2/3 complex genes and the "capping protein ß" (cpb) gene have severely altered the egg phenotype. Arpc1 and cpb RNAi mediated knockdown resulted in the formation of spherical eggs which are devoid of dorsal appendages. Studies also showed the role of Arpc1 and cpb on the number of laid eggs and follicle cell morphology. Furthermore, the depletion of Arpc1 and cpb resulted in a change in F-actin quantity. Together, the data indicate that Arpc1 and cpb regulate Drosophila egg shape, F-actin management, egg-laying characteristics and dorsal appendages formation.

Impairment of α-tubulin and F-actin interactions of GJB3 induces aneuploidy in urothelial cells and promotes bladder cancer cell invasion.

BACKGROUND: We have previously identified an unsuspected role for GJB3 showing that the deficiency of this connexin protein induces aneuploidy in human and murine cells and accelerates cell transformation as well as tumor formation in xenograft models. The molecular mechanisms by which loss of GJB3 leads to aneuploidy and cancer initiation and progression remain unsolved. METHODS: GJB3 expression levels were determined by RT-qPCR and Western blot. The consequences of GJB3 knockdown on genome instability were assessed by metaphase chromosome counting, multinucleation of cells, by micronuclei formation and by the determination of spindle orientation. Interactions of GJB3 with α-tubulin and F-actin was analyzed by immunoprecipitation and immunocytochemistry. Consequences of GJB3 deficiency on microtubule and actin dynamics were measured by live cell imaging and fluorescence recovery after photobleaching experiments, respectively. Immunohistochemistry was used to determine GJB3 levels on human and murine bladder cancer tissue sections. Bladder cancer in mice was chemically induced by BBN-treatment. RESULTS: We find that GJB3 is highly expressed in the ureter and bladder epithelium, but it is downregulated in invasive bladder cancer cell lines and during tumor progression in both human and mouse bladder cancer. Downregulation of GJB3 expression leads to aneuploidy and genomic instability in karyotypically stable urothelial cells and experimental modulation of GJB3 levels alters the migration and invasive capacity of bladder cancer cell lines. Importantly, GJB3 interacts both with α-tubulin and F-actin. The impairment of these interactions alters the dynamics of these cytoskeletal components and leads to defective spindle orientation. CONCLUSION: We conclude that deregulated microtubule and actin dynamics have an impact on proper chromosome separation and tumor cell invasion and migration. Consequently, these observations indicate a possible role for GJB3 in the onset and spreading of bladder cancer and demonstrate a molecular link between enhanced aneuploidy and invasive capacity cancer cells during tumor cell dissemination.

Effects of a Hydrolyzed Lignin Derivative on Bleomycin-Induced Pulmonary Fibrosis in Mice.

Female C57BL/J mice with pulmonary fibrosis induced by injections of bleomycin (20 mg/kg intraperitoneally, 8 times for 4 weeks) were treated with a lignin derivative-based composition BP-C3 (80 mg/kg, daily intragastric administrations for 4 weeks). Bleomycin treatment increased the severity of pulmonary fibrosis (Ashcroft score increased from 1.43±0.20 to 4.17±0.48) and the percentage of α-SMA+ tissue (from 15.22±1.01 to 33.12±2.30%) and DNA-synthetizing nuclei (from 1.05±0.14 to 3.38±0.375). After treatment with BP-C3, we observed a tendency to a decrease in Ashcroft score (to 3.40±0.51) and a significant decrease in the percentage of α-SMA+ tissue to 24.30±1.70%; the percentage of DNA-synthetizing nuclei decreased to a lesser extent (to 3.03±0.22%). These results suggest that BP-C3 has a moderate antifibrotic activity.

Effects of Bulleyaconitine A on Extracellular Matrix Secretion and Expression of Related Proteins in Acetaldehyde-Activated Hepatic Stellate Cells.

Activated hepatic stellate cells differentiate into myofibroblasts, which synthesize and secrete extracellular matrix (ECM) leading to liver fibrosis. It was previously demonstrated that bulleyaconitine A (BLA), an alkaloid from Aconitum bulleyanum, inhibits proliferation and promotes apoptosis of human hepatic Lieming Xu-2 (LX-2) cells. In this study, we analyzed the effect of BLA on the production of ECM and related proteins by LX-2 cells activated with acetaldehyde (AA). The cells were randomized into the control group, AA group (cells activated with 400 µM AA), and BLA+AA group (cells cultured in the presence of 400 µM AA and 18.75 µg/ml BLA). In the BLA+AA group, the contents of collagens I and III and the expression of α-smooth muscle actin and transforming growth factor-ß1 (TGF-ß1) were statistically significantly higher than in the control, but lower than in the AA group. Expression of MMP-1 in the BLA+AA group was also significantly higher than in the AA group, but lower than in the control. Expression of TIMP-1 in the BLA+AA group was significantly higher than in the control, but lower than in the AA group. Thus, BLA suppressed activation and proliferation of LX-2 cells by inhibiting TGF-ß1 signaling pathway and decreasing the content of collagens I and III by reducing the MMP-1/TIMP-1 ratio.

Dexamethasone treatment influences tendon healing through altered resolution and a direct effect on tendon cells.

Inflammation, corticosteroids, and loading all affect tendon healing, with an interaction between them. However, underlying mechanisms behind the effect of corticosteroids and the interaction with loading remain unclear. The aim of this study was to investigate the role of dexamethasone during tendon healing, including specific effects on tendon cells. Rats (n = 36) were randomized to heavy loading or mild loading, the Achilles tendon was transected, and animals were treated with dexamethasone or saline. Gene and protein analyses of the healing tendon were performed for extracellular matrix-, inflammation-, and tendon cell markers. We further tested specific effects of dexamethasone on tendon cells in vitro. Dexamethasone increased mRNA levels of S100A4 and decreased levels of ACTA2/α-SMA, irrespective of load level. Heavy loading + dexamethasone reduced mRNA levels of FN1 and TenC (p < 0.05), while resolution-related genes were unaltered (p > 0.05). In contrast, mild loading + dexamethasone increased mRNA levels of resolution-related genes ANXA1, MRC1, PDPN, and PTGES (p < 0.03). Altered protein levels were confirmed in tendons with mild loading. Dexamethasone treatment in vitro prevented tendon construct formation, increased mRNA levels of S100A4 and decreased levels of SCX and collagens. Dexamethasone during tendon healing appears to act through immunomodulation by promoting resolution, but also through an effect on tendon cells.

Correlation between the expression of the iNOS, caspase-3 and α-SMA genes in the parotid glands of albino rats following the administration of two antihistamines from two different generations.

BACKGROUND: Several medications, including antihistamines, can alter salivary gland function, causing dry mouth or xerostomia. Antihistamines are commonly used for treating allergic rhinitis. OBJECTIVES: The aim of the present study was to compare and correlate the effects of first-generation vs. second-generation H1-antihistamines on the parotid glands of rats. MATERIAL AND METHODS: Twelve adult male albino rats were used; 4 rats served as a control group (group I) and the remaining rats were divided into 2 groups: group II received promethazine hydrochloride; and group III received cetirizine dihydrochloride for 3 weeks. The parotid salivary glands were dissected, and examined histologically and analyzed histomorphometrically for the acinar area percentage. In addition, mRNA gene expression of iNOS, caspase-3 and α-SMA was assessed using quantitative realtime polymerase chain reaction (qRT-PCR). Finally, all the obtained data was statistically analyzed. RESULTS: Histologically, group I showed the typical architecture of the gland. In group II, degenerative changes were noticed, including acinar degeneration and shrinkage with widened connective tissue septa, intracellular vacuolization, and increased inflammatory cell infiltration. In group III, similar histological features were detected as in group II, but to a lesser extent. Histomorphometric results revealed significant differences in the acinar area percentage between various groups. In addition, qRT-PCR results showed a significant increase in iNOS expression in both groups II and III as compared to group I, caspase-3 gene expression was significantly increased in group II, while in group III, it increased non-significantly. Finally, α-SMA gene expression non-significantly decreased in both groups II and III. A significant positive correlation was observed between caspase-3 and iNOS gene expression, while an inverse correlation was noticed between caspase-3 and α-SMA gene expression. CONCLUSIONS: The administration of antihistamines resulted in changes in the rat salivary glands, which could be due to the induction of oxidative stress and the resultant apoptotic effect. These changes were suggested to occur mainly through action on muscarinic receptors; yet, action on histamine receptors could not be excluded. However; these effects were less marked with the second-generation antihistamine.

Long non-coding RNAs in biomarking COVID-19: a machine learning-based approach.

BACKGROUND: The coronavirus pandemic that started in 2019 has caused the highest mortality and morbidity rates worldwide. Data on the role of long non-coding RNAs (lncRNAs) in coronavirus disease 2019 (COVID-19) is scarce. We aimed to elucidate the relationship of three important lncRNAs in the inflammatory states, H19, taurine upregulated gene 1 (TUG1), and colorectal neoplasia differentially expressed (CRNDE) with key factors in inflammation and fibrosis induction including signal transducer and activator of transcription3 (STAT3), alpha smooth muscle actin (α-SMA), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) in COVID-19 patients with moderate to severe symptoms. METHODS: Peripheral blood mononuclear cells from 28 COVID-19 patients and 17 healthy controls were collected. The real-time quantitative polymerase chain reaction (RT-qPCR) was performed to evaluate the expression of RNAs and lncRNAs. Western blotting analysis was also performed to determine the expression levels of STAT3 and α-SMA proteins. Machine learning and receiver operating characteristic (ROC) curve analysis were carried out to evaluate the distinguishing ability of lncRNAs. RESULTS: The expression levels of H19, TUG1, and CRNDE were significantly overexpressed in COVID-19 patients compared to healthy controls. Moreover, STAT3 and α-SMA expression levels were remarkedly increased at both transcript and protein levels in patients with COVID-19 compared to healthy subjects and were correlated with Three lncRNAs. Likewise, IL-6 and TNF-α were considerably upregulated in COVID-19 patients. Machine learning and ROC curve analysis showed that CRNDE-H19 panel has the proper ability to distinguish COVID-19 patients from healthy individuals (area under the curve (AUC) = 0.86). CONCLUSION: The overexpression of three lncRNAs in COVID-19 patients observed in this study may align with significant manifestations of COVID-19. Furthermore, their co-expression with STAT3 and α-SMA, two critical factors implicated in inflammation and fibrosis induction, underscores their potential involvement in exacerbating cardiovascular, pulmonary and common symptoms and complications associated with COVID-19. The combination of CRNDE and H19 lncRNAs seems to be an impressive host-based biomarker panel for screening and diagnosis of COVID-19 patients from healthy controls. Research into lncRNAs can provide a robust platform to find new viral infection-related mediators and propose novel therapeutic strategies for viral infections and immune disorders.

Interferon-γ Induces Interleukin-6 Production and Alpha-smooth Muscle Actin Expression in Systemic Sclerosis Fibroblasts.

Systemic sclerosis (SSc) is an autoimmune systemic disease that is characterized by immune dysregulation, inflammation, vasculopathy, and fibrosis. Tissue fibrosis plays an important role in SSc and can affect several organs such as the dermis, lungs, and heart. Dysregulation of interferon (IFN) signaling contributes to the SSc pathogenesis and interferon regulatory factor 1 (IRF1) has been indicated as the main regulator of type I IFN. This study aimed to clarify the effect of IFN-gamma (-γ) and dexamethasone (DEX) on the IRF1, extracellular signal-regulated kinase 1/2 (ERK1/2), and the expression of alpha-smooth muscle actin (α-SMA) in myofibroblasts and genes involved in the inflammation and fibrosis processes in early diffuse cutaneous systemic sclerosis (dcSSc). A total of 10 early dcSSc patients (diffuse cutaneous form) and 10 unaffected control dermis biopsies were obtained to determine IFNγ and DEX effects on inflammation and fibrosis. Fibroblasts were treated with IFNγ and DEX at optimum time and dose. The expression level of genes and proteins involved in the fibrosis and inflammation processes have been quantified by quantitative real-time PCR (RT-qPCR) and western blot, respectively. IFNγ could up-regulate some of the inflammation-related genes (Interleukin-6; IL6) and down-regulate some of the fibrosis-related genes (COL1A1) in cultured fibroblasts of patients with early dcSSc compared to the untreated group. Besides, it has been revealed that IFNγ can induce fibroblast differentiation to the myofibroblast that expresses α-SMA. Concerning the inhibitory effect of IFNγ on some fibrotic genes and its positive effect on the inflammatory genes and myofibroblast differentiation, it seems that IFNγ may play a dual role in SSc.

Ferrostatin-1 inhibits fibroblast fibrosis in keloid by inhibiting ferroptosis.

Background: Keloid is a chronic proliferative fibrotic disease caused by abnormal fibroblasts proliferation and excessive extracellular matrix (ECM) production. Numerous fibrotic disorders are significantly influenced by ferroptosis, and targeting ferroptosis can effectively mitigate fibrosis development. This study aimed to investigate the role and mechanism of ferroptosis in keloid development. Methods: Keloid tissues from keloid patients and normal skin tissues from healthy controls were collected. Iron content, lipid peroxidation (LPO) level, and the mRNA and protein expression of ferroptosis-related genes including solute carrier family 7 member 11 (SLC7A11), glutathione peroxidase 4 (GPX4), transferrin receptor (TFRC), and nuclear factor erythroid 2-related factor 2 (Nrf2) were determined. Mitochondrial morphology was observed using transmission electron microscopy (TEM). Keloid fibroblasts (KFs) were isolated from keloid tissues, and treated with ferroptosis inhibitor ferrostatin-1 (fer-1) or ferroptosis activator erastin. Iron content, ferroptosis-related marker levels, LPO level, mitochondrial membrane potential, ATP content, and mitochondrial morphology in KFs were detected. Furthermore, the protein levels of α-smooth muscle actin (α-SMA), collagen I, and collagen III were measured to investigate whether ferroptosis affect fibrosis in KFs. Results: We found that iron content and LPO level were substantially elevated in keloid tissues and KFs. SLC7A11, GPX4, and Nrf2 were downregulated and TFRC was upregulated in keloid tissues and KFs. Mitochondria in keloid tissues and KFs exhibited ferroptosis-related pathology. Fer-1 treatment reduced iron content, restrained ferroptosis and mitochondrial dysfunction in KFs, Moreover, ferrostatin-1 restrained the protein expression of α-SMA, collagen I, and collagen III in KFs. Whereas erastin treatment showed the opposite results. Conclusion: Ferroptosis exists in keloid. Ferrostatin-1 restrained ECM deposition and fibrosis in keloid through inhibiting ferroptosis, and erastin induced ECM deposition and fibrosis through intensifying ferroptosis.

A Lifeact-EGFP quail for studying actin dynamics in vivo.

Here, we report the generation of a transgenic Lifeact-EGFP quail line for the investigation of actin organization and dynamics during morphogenesis in vivo. This transgenic avian line allows for the high-resolution visualization of actin structures within the living embryo, from the subcellular filaments that guide cell shape to the supracellular assemblies that coordinate movements across tissues. The unique suitability of avian embryos to live imaging facilitates the investigation of previously intractable processes during embryogenesis. Using high-resolution live imaging approaches, we present the dynamic behaviors and morphologies of cellular protrusions in different tissue contexts. Furthermore, through the integration of live imaging with computational segmentation, we visualize cells undergoing apical constriction and large-scale actin structures such as multicellular rosettes within the neuroepithelium. These findings not only enhance our understanding of tissue morphogenesis but also demonstrate the utility of the Lifeact-EGFP transgenic quail as a new model system for live in vivo investigations of the actin cytoskeleton.

NLRP4E regulates actin cap formation through SRC and CDC42 during oocyte meiosis.

BACKGROUND: Members of the nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain containing (NLRP) family regulate various physiological and pathological processes. However, none have been shown to regulate actin cap formation or spindle translocation during the asymmetric division of oocyte meiosis I. NLRP4E has been reported as a candidate protein in female fertility, but its function is unknown. METHODS: Immunofluorescence, reverse transcription polymerase chain reaction (RT-PCR), and western blotting were employed to examine the localization and expression levels of NLRP4E and related proteins in mouse oocytes. small interfering RNA (siRNA) and antibody transfection were used to knock down NLRP4E and other proteins. Immunoprecipitation (IP)-mass spectrometry was used to identify the potential proteins interacting with NLRP4E. Coimmunoprecipitation (Co-IP) was used to verify the protein interactions. Wild type (WT) or mutant NLRP4E messenger RNA (mRNA) was injected into oocytes for rescue experiments. In vitro phosphorylation was employed to examine the activation of steroid receptor coactivator (SRC) by NLRP4E. RESULTS: NLRP4E was more predominant within oocytes compared with other NLRP4 members. NLRP4E knockdown significantly inhibited actin cap formation and spindle translocation toward the cap region, resulting in the failure of polar body extrusion at the end of meiosis I. Mechanistically, GRIN1, and GANO1 activated NLRP4E by phosphorylation at Ser429 and Thr430; p-NLRP4E is translocated and is accumulated in the actin cap region during spindle translocation. Next, we found that p-NLRP4E directly phosphorylated SRC at Tyr418, while p-SRC negatively regulated p-CDC42-S71, an inactive form of CDC42 that promotes actin cap formation and spindle translocation in the GTP-bound form. CONCLUSIONS: NLRP4E activated by GRIN1 and GANO1 regulates actin cap formation and spindle translocation toward the cap region through upregulation of p-SRC-Tyr418 and downregulation of p-CDC42-S71 during meiosis I.

KLF4 Inhibits the Activation of Human Hepatic Stellate Cell In Vitro.

OBJECTIVE: Hepatic stellate cells (HSCs) play a crucial role in liver fibrosis. Early-stage liver fibrosis is reversible and intimately associated with the state of HSCs. Kruppel-like factor 4 (KLF4) plays a pivotal role in a wide array of physiological and pathological processes. This study aimed to investigate the effect of KLF4 on the proliferation, apoptosis and phenotype of quiescent HSCs METHODS: We designed a KLF4 lentiviral vector and a KLF4 siRNA lentiviral vector, to upregulate and silence KLF4 expression in human HSC LX-2 cells via transfection. Cell proliferation was assessed using the CCK-8 assay. Flow cytometry was used to detect the cell cycle distribution and apoptosis rate. Western blotting was used to determine the levels of some quiescence and activation markers of HSCs RESULTS: Overexpression of KLF4 significantly increased the levels of E-cadherin and ZO-1, which are quiescent HSC markers, while significantly decreased the levels of N-cadherin and a-SMA, known activated HSC markers. In contrast, cell proliferation and apoptosis rates were elevated in LX-2 cells in which KLF4 expression was silenced CONCLUSION: KLF4 inhibits the proliferation and activation of human LX-2 HSCs. It might be a key regulatory protein in the maintenance of HSC quiescence and may serve as a target for the inhibition of hepatic fibrosis.

Characterization of Actin-based Genotypes and Mycoplasma Endosymbionts of Trichomonas vaginalis Isolated in Sapporo, Japan.

PURPOSE: Trichomonas vaginalis is a causative agent of common non-viral sexually transmitted infections worldwide. However, the biological features, such as genotypes and endosymbionts, of T. vaginalis isolated in Japan remain unclear. The aim of this study was to characterize the actin-based genotypes and the endosymbionts of T. vaginalis isolated in Sapporo, Japan. METHODS: Three T. vaginalis clinical strains were isolated in Sapporo, Japan between 2019 and 2022. Actin-based genotyping was conducted by sequencing and phylogenetic analyses. The endosymbionts, such as Mycoplasma sp. and Trichomonasvirus, were detected using PCR and RT-PCR, respectively. Furthermore, the detected Mycoplasma spp. were identified using 16S rRNA gene sequencing. RESULTS: Of the three T. vaginalis strains, two belonged to genotype E, whereas one was genotype G as determined by actin-based genotyping. Two of the T. vaginalis strains harbored Mycoplasma spp. Using nearly full-length 16S rRNA gene sequencing, both were identified as Candidatus Mycoplasma girerdii. In contrast, the Trichomonasvirus was not found in the T. vaginalis strains. CONCLUSION: To our knowledge, this is the first report on the characterization of actin-based genotypes and the presence of endosymbiotic Ca. M. girerdii in T. vaginalis strains in Japan. Thus, this study will provide an important impetus for future research.

Prolonged depletion of profilin 1 or F-actin causes an adaptive response in microtubules.

In addition to its well-established role in actin assembly, profilin 1 (PFN1) has been shown to bind to tubulin and alter microtubule growth. However, whether PFN1's predominant control over microtubules in cells occurs through direct regulation of tubulin or indirectly through the polymerization of actin has yet to be determined. Here, we manipulated PFN1 expression, actin filament assembly, and actomyosin contractility and showed that reducing any of these parameters for extended periods of time caused an adaptive response in the microtubule cytoskeleton, with the effect being significantly more pronounced in neuronal processes. All the observed changes to microtubules were reversible if actomyosin was restored, arguing that PFN1's regulation of microtubules occurs principally through actin. Moreover, the cytoskeletal modifications resulting from PFN1 depletion in neuronal processes affected microtubule-based transport and mimicked phenotypes that are linked to neurodegenerative disease. This demonstrates how defects in actin can cause compensatory responses in other cytoskeleton components, which in turn significantly alter cellular function.

CXCR3 participates in asymmetric division of mouse oocytes by modulating actin dynamics.

Extensive research has been conducted on the role of CXCR3 in immune responses and inflammation. However, the role of CXCR3 in the reproductive system, particularly in oocyte development, remains unknown. In this study, we present findings on the involvement of CXCR3 in the meiotic division process of mouse oocytes. We found CXCR3 was expressed consistently throughout the entire maturation process of mouse oocyte. Inhibition of CXCR3 impaired the asymmetric division of oocyte, while the injection of Cxcr3 mRNA was capable of restoring these defects. Further study showed that inhibition of CXCR3 perturbed spindle migration by affecting LIMK/cofilin pathway-mediated actin remodeling. Knockout of CXCR3 led to an upregulation of actin-binding protein and an increased ATP level in GV-stage oocytes, while maintaining normal actin dynamics during the process of meiosis. Additionally, we noticed the expression level of DYNLT1 is markedly elevated in CXCR3-null oocytes. DYNLT1 bound with the Arp2/3 complex, and knockdown of DYNLT1 in CXCR3-null oocytes impaired the organization of cytoplasmic actin, suggesting the regulatory role of DYNLT1 in actin organization, and the compensatory expression of DYNLT1 may contribute to maintain normal actin dynamics in CXCR3-knockout oocytes. In summary, our findings provide insights into the intricate network of actin dynamics associated with CXCR3 during oocyte meiosis.

A Potential Combination of Targeting HSP90 and mTOR in Breast Cancer Cell Growth, Migration, and Invasion Through Inhibiting AKT Phosphorylation and F-actin Organization.

BACKGROUND/AIM: Breast cancer is the most prevalent form of cancer among women worldwide, with a high mortality rate. While the most common cause of breast cancer death is metastasis, there is currently no potential treatment for patients at the metastatic stage. The present study investigated the potential of using a combination of HSP90 and mTOR inhibitor in the treatment of breast cancer cell growth, migration, and invasion. MATERIALS AND METHODS: Gene Expression Profiling Interactive Analysis (GEPIA) was used to investigate the gene expression profiles. Western blot analysis and fluorescence staining were used for protein expression and localization, respectively. MTT, wound healing, and transwell invasion assays were used for cell proliferation, migration, and invasion, respectively. RESULTS: GEPIA demonstrated that HSP90 expression was significantly higher in breast invasive carcinoma compared to other tumor types, and this expression correlated with mTOR levels. Treatment with 17-AAG, an HSP90 inhibitor, and Torkinib, an mTORC1/2 inhibitor, significantly inhibited cell proliferation. Moreover, combination treatment led to down-regulation of AKT. Morphological changes revealed a reduction in F-actin intensity, a marked reduction of YAP, with interference in nuclear localization. CONCLUSION: Targeting HSP90 and mTOR has the potential to suppress breast cancer cell growth and progression by disrupting AKT signaling and inhibiting F-actin polymerization. This combination treatment may hold promise as a therapeutic strategy for breast cancer treatment that ameliorates adverse effects of a single treatment.

Molecular mechanisms linking missense ACTG2 mutations to visceral myopathy.

Visceral myopathy is a life-threatening disease characterized by muscle weakness in the bowel, bladder, and uterus. Mutations in smooth muscle γ-actin (ACTG2) are the most common cause of the disease, but the mechanisms by which the mutations alter muscle function are unknown. Here, we examined four prevalent ACTG2 mutations (R40C, R148C, R178C, and R257C) that cause different disease severity and are spread throughout the actin fold. R178C displayed premature degradation, R148C disrupted interactions with actin-binding proteins, R40C inhibited polymerization, and R257C destabilized filaments. Because these mutations are heterozygous, we also analyzed 50/50 mixtures with wild-type (WT) ACTG2. The WT/R40C mixture impaired filament nucleation by leiomodin 1, and WT/R257C produced filaments that were easily fragmented by smooth muscle myosin. Smooth muscle tropomyosin isoform Tpm1.4 partially rescued the defects of R40C and R257C. Cryo-electron microscopy structures of filaments formed by R40C and R257C revealed disrupted intersubunit contacts. The biochemical and structural properties of the mutants correlate with their genotype-specific disease severity.

The actin-binding protein CAP1 represses MRTF-SRF-dependent gene expression in mouse cerebral cortex.

Serum response factor (SRF) is an essential transcription factor for brain development and function. Here, we explored how an SRF cofactor, the actin monomer-sensing myocardin-related transcription factor MRTF, is regulated in mouse cortical neurons. We found that MRTF-dependent SRF activity in vitro and in vivo was repressed by cyclase-associated protein CAP1. Inactivation of the actin-binding protein CAP1 reduced the amount of actin monomers in the cytoplasm, which promoted nuclear MRTF translocation and MRTF-SRF activation. This function was independent of cofilin1 and actin-depolymerizing factor, and CAP1 loss of function in cortical neurons was not compensated by endogenous CAP2. Transcriptomic and proteomic analyses of cerebral cortex lysates from wild-type and Cap1 knockout mice supported the role of CAP1 in repressing MRTF-SRF-dependent signaling in vivo. Bioinformatic analysis identified likely MRTF-SRF target genes, which aligned with the transcriptomic and proteomic results. Together with our previous studies that implicated CAP1 in axonal growth cone function as well as the morphology and plasticity of excitatory synapses, our findings establish CAP1 as a crucial actin regulator in the brain relevant for formation of neuronal networks.

Tail length and E525K dilated cardiomyopathy mutant alter human ß-cardiac myosin super-relaxed state.

Dilated cardiomyopathy (DCM) is a condition characterized by impaired cardiac function, due to myocardial hypo-contractility, and is associated with point mutations in ß-cardiac myosin, the molecular motor that powers cardiac contraction. Myocardial function can be modulated through sequestration of myosin motors into an auto-inhibited "super-relaxed" state (SRX), which may be further stabilized by a structural state known as the "interacting heads motif" (IHM). Here, we sought to determine whether hypo-contractility of DCM myocardium results from reduced function of individual myosin molecules or from decreased myosin availability to interact with actin due to increased IHM/SRX stabilization. We used an established DCM myosin mutation, E525K, and characterized the biochemical and mechanical activity of wild-type and mutant human ß-cardiac myosin constructs that differed in the length of their coiled-coil tail, which dictates their ability to form the IHM/SRX state. We found that short-tailed myosin constructs exhibited low IHM/SRX content, elevated actin-activated ATPase activity, and fast velocities in unloaded motility assays. Conversely, longer-tailed constructs exhibited higher IHM/SRX content and reduced actomyosin ATPase and velocity. Our modeling suggests that reduced velocities may be attributed to IHM/SRX-dependent sequestration of myosin heads. Interestingly, longer-tailed E525K mutants showed no apparent impact on velocity or actomyosin ATPase at low ionic strength but stabilized IHM/SRX state at higher ionic strength. Therefore, the hypo-contractility observed in DCM may be attributable to reduced myosin head availability caused by enhanced IHM/SRX stability in E525K mutants.